1. Field of the Invention
This disclosure relates generally to mechanical and/or electro-mechanical power modulation devices and methods, and more particularly to continuously and/or infinitely variable, planetary power modulating devices and methods for providing auxiliary air conditioning, heating, and power to a vehicle.
2. Description of the Related Art
Auxiliary power units are often used in cross-country trucks that are equipped with a sleeper compartment located behind a truck cab so that the driver has a convenient place to sleep while in route. An Auxiliary Power Unit (APU) allows the driver to use its truck amenities like heat, air conditioning, microwave, television, etc. without running the engine, which reduces emissions. See, for example, U.S. Pat. No. 5,333,678 to Mellum. APUs are also used extensively in refrigerated trailers for maintaining cargo temperatures during transport and delivery.
APUs have become significantly more important in the heavy duty trucking industry because the Environmental Protection Agency (EPA) and the California Air Resource Board (CARB) have been developing and passing regulations that impact idling in an attempt to reduce emissions and pollution. The passage of these different regulations has impacted the trucking industry. In particular, it has affected the heavy duty (Class 8) sleeper tractor drivers who typically idle their vehicle for many hours each day. It is estimated that drivers are on the road five days per week. The federal law states that drivers are only allowed to be on the road a maximum of 14 hours a day with 10 hours down time required. Therefore, the sleeper cab industry has a large potential for APUs to reduce idling during the required downtime. Over half of the states in the U.S. have anti-idling regulations in place, and this number is projected to increase as more states adopt CARB regulations. Beyond the numerous federal and state regulations against idling, the industry is also facing idling regulations at the local and municipal levels as well. While their regulations vary by location, they all prohibit trucks from idling over three to five minutes. Some industry experts believe that the environmental agencies are gaining momentum in their initiative to put more pressure on the Federal government as well as on states to make the idling regulations even more stringent in the coming years. If the environmental agencies succeed, some form of anti-idling technology (not just APUs) will become a necessity for truck drivers expanding beyond Class 8 sleeper tractors.
The rise and fall of diesel fuel prices continues to play a role in the adoption of idle reduction technology as users (particularly fleets) seek to lower their fuel consumption especially when diesel prices are high. When diesel fuel prices reached an all time high in 2008, demand for idle reduction technology increased because of the roughly 8% fuel savings they offer. In the long run, most industry experts expect diesel fuel prices to rise, which will again spark interest in APUs as they help to reduce fuel consumption as well as reducing wear and tear on the engine.
In most commercially available APU systems, a single power source drives multiple devices. The power source typically has a narrow operating speed range at which the performance of the power source is optimum. It is preferred to operate the power source within its performance optimizing operating speed range. A driven device typically also has a narrow operating speed range at which the performance of the driven device is optimum. It is also preferred to operate the driven device within its performance optimizing operating speed range. A coupling is usually employed to transfer power from the power source to the driven device. Where a direct, non-modulating coupling couples the power source to the driven device, the driven device operates at a speed proportional to that of the power source. However, it is often the case that the optimum operating speed of the driven device is not directly proportional to the optimum operating speed of the power source. Therefore, it is preferred to incorporate into the system a coupling adapted to modulate between the speed of the power source and the speed of the driven device.
Couplings between the power source and the driven devices can be selected such that the input speed from the power source is reduced or increased at the output of a given coupling. However, in frequently implemented systems, typical known power train configurations and/or coupling arrangements allow at best for a constant ratio between the input speed from the power source and the speed of power transfer to the driven device. The result of such system configuration is that often any given accessory does not operate within its maximum efficiency speed range. Consequently, inefficiencies arise from wasted energy during operation and over sizing of the accessories to handle the speed and/or torque ranges.
Thus, there exists a continuing need for devices and methods to modulate power transfer between a prime mover and driven devices. In some APU systems, it would be beneficial to regulate the speed and/or torque transfer from an internal combustion engine to one or more driven devices that operate at varying efficiency optimizing speeds. The inventive embodiments of power modulating devices and/or drivetrains described below address one or more of these needs.